Device and process for the production offine fat particles

ABSTRACT

A device and to a process which can be carried out using the device, for the production of fine particles from a liquid which solidifies upon cooling, in particular from liquid fat. The process has the advantage of producing fine particles of very small size, preferably with narrow size distribution. The device has the advantage that a solidifying liquid can be supplied at a temperature above its solidification temperature, without cooling gas leading to solidification of the liquid in the supply line, which cooling gas is used in the production of the particles.

The present invention relates to a device and to a process, which canespecially be carried out by use of the device, for the production offine particles from a liquid which solidifies upon cooling, inparticular from liquid fat which has a temperature above itssolidification temperature and which solidifies upon cooling.

The process has the advantage of producing fine particles of very smallsize, preferably with a narrow size distribution. The device has theadvantage that a solidifying liquid can be supplied at a temperatureabove its solidification temperature without cooling gas resulting insolidification of the liquid in the supply line, which cooling gas isused in the generation of the particles. By means of a cooling gas whichis introduced into a nozzle as a propellant gas, and preferably bysubsequently introducing the mixture of the liquid and propellant gas,or resp. of fat and propellant gas, which mixture exits from a nozzle,into a space with cooled gas, the liquid is solidified, forming fineparticles. Therein, the propellant gas has a temperature below thesolidification temperature of the liquid or of the fat.

STATE OF THE ART

U.S. Pat. No. 4,952,224 A for the production of fat particles describesthe spraying of hot liquid fat through a heated Venturi nozzle and thesubsequent blowing onto the spray jet in the same direction of itsmovement, with nitrogen or carbon dioxide as a cooling gas.

OBJECT OF THE INVENTION

The invention has the object to provide an alternative device and analternative process for the production of fine particles from a liquidwhich solidifies upon cooling. The device and process shall especiallybe suitable for the production of fine particles with a narrow sizedistribution and without larger droplets.

DESCRIPTION OF THE INVENTION

The invention achieves the object by the features of the claims and inparticular by means of a process and by a device having a nozzle, to theinlet opening of which nozzle, which inlet opening is arranged at thefirst end, a propellant gas supply line is connected, and to the inletopening of which nozzle a supply line discharges for the liquid, whichis in particular liquid fat. The supply line preferably discharges inthe area of the nozzle in which negative pressure is generated uponapplication of propellant gas onto the propellant gas supply line. Thepropellant gas supply line can be formed in the form of at least 2 or atleast 3, more preferably at least 8 lines which are distributed aroundthe longitudinal axis of the nozzle, even more preferably by an annularmouth of the supply line.

The nozzle has a central channel which at its first end forms an inletopening which is spanned open by a convex face about the longitudinalaxis of the central channel, and at its opposite second end forms anoutlet opening. Generally, the central channel, which is spanned open bythe face that is convex to the longitudinal axis, tapers from the inletopening to a section in which the central channel has the smallestradius. The convex face preferably extends rotationally symmetricallyabout the longitudinal axis of the central channel and particularlypreferably has a convex surface which extends radially about thelongitudinal axis of the central channel, wherein the surface can e.g.be parabolic, the slope of which surface increases in the directiontowards the longitudinal axis of the central channel, i.e. the slope ofwhich surface increases with decreasing radius to form a curvature whichis increasing towards the longitudinal axis. The nozzle can extend onlyover a first section between the inlet opening and its smallest radius,such that the nozzle terminates in its smallest radius, respectivelysuch that the central channel terminates in its smallest radius andspans open the outlet opening. In this embodiment, the nozzle is anon-extended nozzle.

Alternatively and preferably, the central channel of the nozzle adjacentto its first section adjacent to its smallest radius has a secondsection which widens from this smallest radius in the direction towardsthe outlet opening, preferably with a conically increasingcross-section. Therein, the second section can span open the outletopening e.g. maximally up to a distance from the section of the smallestradius, in which no jet separation from the central channel occurs. Thesecond section can e.g. have a length that is the length of the firstsection along the longitudinal axis by a factor of 0.2 or 0.5 or 0.6 toa maximum of a factor of 2 or 1.6 or 1. In this embodiment, the nozzleis a Laval nozzle, the second section of which discharges into theoutlet opening within or ahead of the area of the jet separation.

In cooperation with the increasing diameter of the central channel inthe section which is adjacent to its section having the smallest radiusadjacent to the convex face, a negative pressure is generated which actsas far as into the inlet opening, more preferably into the plane inwhich the propellant gas supply line opens.

The propellant gas supply line is arranged to allow propellant gas toflow out into the inlet opening approximately in parallel to the surfaceof the central channel, so that the propellant gas supply line is set upto allow compressed air flowing radially with respect to thelongitudinal axis of the central channel to flow against the surface.

Preferably, the propellant gas supply line forms an annular supply linehaving an annular opening at the inlet opening of the central channel.Therein, the annular opening of the supply line is limited by thesurface of the central channel, which surface spans open the inletopening of the central channel. At a distance from the surface of thecentral channel, the annular opening is formed e.g. by a shoulder thatis spaced from the convex face so that the cross-section of the annularopening is arranged in a section adjacent to the inlet opening of thecentral channel, wherein the inlet opening directly abuts to the inletopening or is spaced by an axial section of the longitudinal axis of thecentral channel. The shoulder is preferably annular so that it forms,together with the spaced convex face spanning open the inlet opening, anannular opening of the propellant gas supply line about the longitudinalaxis of the central channel.

Connected to the propellant gas supply line is a source of propellantgas, which is preferably propellant gas that is cooled to a temperatureof at least 50 K below, more preferably at least 100 K below thesolidification temperature of the liquid, especially below thesolidification temperature of the liquid fat, e.g. a container forcooled propellant gas, e.g. for liquid nitrogen or for gaseous nitrogenthat is produced directly from liquid nitrogen, or a compressor and acooling device for propellant gas.

The propellant gas that enters the nozzle is cooled, especially to atemperature of at least 50 K or at least 100 K below the solidificationtemperature of the liquid fat. The propellant gas can e.g. have atemperature of −60° C. to −90° C. for palm fat or coconut fat as aliquid fat that can e.g. have a temperature of 40° C. to 50° C.

Surprisingly, it has shown that propellant gas, which is used inspraying liquid fat and which has a temperature of at least 50 K or atleast 100 K below the solidification temperature of the liquid fat,leads to the production of fine particles, and that no or no disturbingdeposits of the fat occur in the nozzle, which is in particular a Lavalnozzle. Optionally, the nozzle is heated. Therein, it has shown thatheating the nozzle has little or no impairing effect on the productionof fine fat particles when the propellant gas is at least 50 K or atleast 100 K colder than the solidification temperature of the fat.

Generally, the mouth of the liquid supply line can be located in an areain which the nozzle generates a negative pressure relative to theambient pressure or relative to the pressure of the propellant gas uponapplication of propellant gas to the propellant gas supply line. Thisarea in which negative pressure is generated can extend from a distancefrom the inlet opening to the area with the smallest radius of thecentral channel, or can extend from the area in which the propellant gassupply line discharges up to the area of the inlet opening of thecentral channel or up to the area of the smallest radius of the centralchannel.

The arrangement of the propellant gas supply line such that it opensradially to the longitudinal axis of the central channel at the inletopening, in particular in an annular opening, guides the propellant gasalong the surface of the central channel and generates a gas flowlongitudinally along the central channel. At its first end, the nozzlecan be open to the environment and can form an supply air opening, suchthat gas from the environment can be drawn into the inlet openingthrough the supply air opening. Between the liquid supply line and thecentral channel, the nozzle can e.g. have a supply air opening that isopen to the environment. Optionally, gas, e.g. propellant gas which isrecirculated after flowing out of the outlet opening, can be guided tothe supply air opening. This embodiment has the advantage that thepropellant gas draws in gas from the surroundings through the supply airopening and the gas volume flow through the nozzle is amplified at thesame volume flow of the propellant gas. Optionally, gas which issupplied to the supply air opening can be temperature-controlled to atemperature between room temperature and the temperature that the liquidhas in its supply line, or above its solidification temperature.Preferably, the device generally has a cooling device for cooling thegas which is supplied to the supply air opening, e.g. to the temperatureof the propellant gas which is supplied to the nozzle, e.g. −90 to −60°C. The gas which is supplied to the supply air opening, e.g. via aconduit, can be recirculated propellant gas which has flowed out of thenozzle, and preferably after separation of particles, e.g. via acyclone, a membrane, or a deep-bed filter.

Alternatively, the nozzle can be closed between the propellant gassupply line and the liquid supply line, so that only the propellant gassupply line and the liquid supply line are connected to the inletopening, respectively the nozzle has no supply air opening.

The propellant gas preferably is cooled gas, preferably inert gas, e.g.nitrogen and/or CO₂. The propellant gas is cooled to a temperature,determined after the exit from the propellant gas supply line, whichtemperature is sufficient to cool the liquid to a temperature below itssolidification temperature. Preferably, the propellant gas is cooled toa temperature of at least 50 K, preferably of at least 75 K or of atleast 100 K, preferably of at least 150 K below the temperature of theliquid in the liquid supply line, or below the solidificationtemperature of the liquid. Particularly preferably, the propellant gasis nitrogen having a temperature of −196° C. to −60° C., which is e.g.produced by immediately preceding evaporation of liquid nitrogen.

The liquid has a temperature above its solidification temperature, e.g.10 K to 100 K, or 20 to 50 K above its solidification temperature atambient pressure.

It has shown that supplying the liquid into the area of the nozzle wherenegative pressure is generated by inflowing propellant gas results inintensive mixing of the liquid fat with the colder propellant gas and inthe formation of fine droplets that can solidify into particles.

Preferably, the supply line for the liquid fat is heatable, e.g. isheated continuously or in a controlled manner only at the beginning ofthe process, is not heated during the process and/or is heated only atthe end of the process, in order to avoid solidification of the liquidin the supply line.

Optionally, the nozzle can be heatable, e.g. in the area extendingbetween its inlet opening and the area of the smallest radius, and/or inthe optional area extending between the area of the smallest radius andthe outlet opening, e.g. heatable to a temperature above thesolidification temperature of the liquid fat and e.g. below thevaporization temperature of the liquid fat. For fats which are solid atroom temperature, the nozzle and/or the supply line can e.g. be heatedto 150 to 250° C., e.g. to 180 to 220° C., e.g. to 200° C. A heatablenozzle has the advantage of liquefying or vaporizing fat which isdeposited on the central channel during the process, so that this fat issubsequently cooled to particles by the propellant gas. The nozzleand/or the liquid supply line can be heatable in that it contains, on orin its wall, electrical heating elements or channels for the passage ofa heat transfer medium.

The nozzle discharges into a gas space which has a temperature below thesolidification temperature of the liquid, which preferably is liquidfat, e.g. a temperature of at least 50 K, preferably at least 75 K or atleast 100 K, preferably at least 150 K or at least 200 K, below thesolidification temperature of the liquid. This is because it has shownthat the nozzle disperses the liquid into fine droplets which thensolidify in the gas space at a lower temperature. This dispersion of theliquid into fine droplets is currently attributed to the propellant gascausing effective shearing of the liquid in the nozzle, which ispreferably a Laval nozzle, while at the same time the colder propellantgas leads to the expansion of the liquid fat and to the prevention ofsubsequent coalescence.

Therein, the inlet opening of the nozzle can be arranged outside of thisgas space. Preferably, the propellant gas is cooled, e.g. to atemperature of at least 50 K, preferably at least 75 K or at least 100K, preferably at least 150 K or at least 200 K below the solidificationtemperature of the liquid. Therein, the nozzle can draw in gas from theenvironment through its inlet opening 3 or through the supply airopening 14, which gas is cooled by mixing with the propellant gas.

In a preferred embodiment, the device has a counterflow unit that is setup to direct a gas flow against the gas flow exiting from the outletopening of the nozzle. A counterflow unit can direct the gas flow, whichcan be a single gas flow or which can have at least two partial flows,frontally or at an angle of e.g. 90° to 180° onto the gas flow exitingfrom the nozzle. The counterflow unit preferably supplies cooled gas,e.g. cooled at a temperature, which is determined after the exit fromthe counterflow unit, of at least 50 K, preferably at least 75 K or atleast 100 K, preferably at least 150 K below the temperature of theliquid in the liquid supply line, or below the solidificationtemperature of the liquid.

The counterflow unit generates a counterflow of cooled gas, whichcounterflow can consist of one counterflow or of at least two partialcounterflows, e.g. directed at an angle of 90° to 180° against the gasflow exiting from the nozzle. Therein, the gas flow exiting from thenozzle has particles and preferably has droplets of liquid not yetsolidified, in particular of liquid fat not yet solidified. Generally,the counterflow unit can be connected to a supply line that conductscooled propellant gas which is taken from the gas flow exiting from thenozzle, preferably after compression and cooling.

In the process, the counterflow unit generates at least one gas flowwhich is directed against the gas flow exiting from the nozzle. It hasshown that a process in which cooled gas from a counterflow unit isdirected in counterflow against the gas flow exiting from the nozzleresults in the production of smaller particles and/or in the productionof particles of a narrower size distribution from the liquid, inparticular from liquid fat. Currently, it is assumed that the at leastone cooled gas flow, which is directed from the counterflow unit towardsthe gas flow exiting from the nozzle, leads to the shearing of liquiddroplets and to the vaporization of liquid droplets with formation ofsmaller particles and/or with a narrower size distribution of particlesthan the process without counterflow.

Preferably, in the process, particles, in particular of fat, areproduced by cooling from a liquid, in particular from liquid fat, whichliquid has a temperature above its solidification temperature, whereinthe liquid is passed through a supply line into the area of the nozzlein which negative pressure is generated, while propellant gas is guidedthrough the propellant gas supply line to the inlet opening of thenozzle, wherein the propellant gas is cooled, e.g. having a temperatureof at least 50 K, preferably at least 100 K below the solidificationtemperature, with flowing through the central channel of the nozzle,which tapers to a section of smallest radius, and discharging of thepropellant gas, which is in admixture with the cooled liquid, from anoutlet opening of the nozzle, which outlet opening lies opposite to theinlet opening, and separation of particles from the propellant gas. Theparticles are therefore formed from the liquid that has solidified bycooling, optionally with propellant gas enclosed, or the particlesconsist of the liquid that has solidified by cooling.

The liquid is e.g. fat, in particular palm fat, coconut fat or anotherplant-based fat.

Preferably, the nozzle is vertical with its outlet opening directedupward, a counterflow unit is preferably directed against the outletopening.

The invention is now described in more detail with reference to theFigures, which schematically show

In FIG. 1 an embodiment of the device according to the invention in topview onto the outlet opening,

In FIG. 2 the embodiment of FIG. 1 in section A-A,

In FIG. 3 an embodiment in perspective top view, and

In FIG. 4 the embodiment of FIG. 3 in section A-A.

FIGS. 1 to 4 show a nozzle having a rotationally symmetrical centralchannel 1 that tapers from an inlet opening 3, which is arranged at thefirst end 2, to a section 4 having the smallest radius 5 of the centralchannel 1. In the embodiment shown, the central channel 1 has a firstsection 6 which extends from the inlet opening 3 to the section 4 havingthe smallest radius 5, and has an adjacent second section 7 in which thecentral channel 1 widens from the section 4 having the smallest radius 5to the outlet opening 8 which is spanned open by the central channel 1at the second end 9. The central channel has a face that is convex toits longitudinal axis.

At the first end 2 of the central channel 1, an annular opening 10 isformed between the inlet opening 3 and an annular shoulder 11. Apropellant gas supply line 12 is connected to the annular opening 10 forsupplying propellant gas. Optionally, the propellant gas supply line 12can be supplied with recirculated propellant gas which is drawn from thegas exiting from the nozzle, e.g. by means of a compressor (not shown),wherein e.g. particles are separated from the gas by means of aseparating device (not shown), and the gas is cooled by means of acooling device (not shown). Alternatively, the propellant gas cangenerally come from a pressure vessel (not shown).

A supply line 13 for directing the liquid into the nozzle discharges inthe area of the nozzle in which negative pressure is generated by thepropellant gas, in this case at a short distance in front of the planeof the annular opening 10 or resp. in front of the inlet opening 3. Thesupply line 13 can be heatable, e.g. electrically, by means of acontrolled heater (not shown).

In the embodiment shown here, the distance between the supply line 16for the liquid and the annular shoulder 11, which limits the annularopening 10, forms a supply air opening 14 through which gas from thesurroundings can be drawn into the nozzle. Therein, recirculatedpropellant gas can be directed to the supply air opening 14 by means ofa conduit (not shown), alternatively, the supply air opening can beclosed or can be accessible only to a connected conduit (not shown) thatsupplies recirculated propellant gas.

In accordance with a preferred embodiment, FIGS. 3 and 4 show acounterflow unit 20 which, by way of example, allows 4 partial flows toexit from outlets 21, which are directed against the gas flow exitingfrom the outlet opening 8. Preferably, a conduit leads propellant gas,which is extracted from the gas flow exiting from the nozzle, to thecounterflow unit 20 after separation of particles, preferably afterpassing through a compressor and a cooling device.

EXAMPLE Production of Fine Fat Particles from Liquid Fat

As a representative of a liquid, coconut fat at a temperature of 80 to90° C. was directed through a supply line of a device that generallycorresponded to FIGS. 3 and 4. As a propellant gas, nitrogen,immediately after the evaporation of liquid nitrogen, was directedthrough the annular opening 10 and was flowed along the convex face ofthe central channel 1 to the inlet opening 3. The gaseous nitrogen whichwas used as propellant gas had a temperature of about −60 to −90° C. Theoutlet opening could be open to the surroundings. Particles of fathaving a small particle size were produced. The supply line was heatedto approx. 90 to 100° C.

To prevent deposits of the fat within the nozzle, this was heated toabout 200° C.

Additionally, in one variant, nitrogen, also immediately after theevaporation of liquid nitrogen, was directed through a single outlet 21,in perpendicular against the outlet opening 8 of the nozzle. The outlet21 was arranged at a distance of approx. 1 to 5 cm from the outletopening 8.

REFERENCE NUMERAL

1 central channel

2 first end

3 inlet opening

4 section

5 smallest radius

6 first section

7 second section

8 outlet opening

9 second end

10 annular opening

11 annular shoulder

12 propellant gas supply line

13 liquid supply line

14 supply air opening

20 counterflow unit

21 outlet

1. Process for producing particles from liquid fat having a temperatureabove its solidification temperature, by cooling, wherein the liquid fatis conducted through a supply line into the area of a nozzle, in whicharea negative pressure is generated, while propellant gas is directed tothe inlet opening of the nozzle, flowing through of the central channelof the nozzle, which central channel tapers to a section of smallestradius, and discharging the mixture of the propellant gas with the fatfrom an outlet opening of the nozzle which lies opposite to the inletopening, wherein the propellant gas has a temperature of at least 50 Kbelow the solidification temperature of the liquid fat, with subsequentcooling of the mixture of the propellant gas with the fat and removingparticles from the propellant gas.
 2. Process according to claim 1,wherein, subsequent to the central channel which tapers to a section ofsmallest radius, a second section of the central channel is flowedthrough, in which second section the central channel widens to theoutlet opening.
 3. Process according to claim 1, wherein the centralchannel, which is spanned open by the face that is convex to thelongitudinal axis, tapers from the inlet opening to a section in whichthe central channel has its smallest radius and is spanned open by aconvex face which extends radially about the longitudinal axis of thecentral channel and which extends rotationally symmetrically about thelongitudinal axis of the central channel
 4. Process according to claim1, wherein the propellant gas supply line forms an annular supply linehaving an annular opening at the inlet opening of the central channel,and the annular opening of the supply line is limited by the surface ofthe central channel, which surface spans open the inlet opening of thecentral channel.
 5. Process according to claim 1, wherein the cooling ofthe mixture of the propellant gas with the liquid occurs by the mixtureof the propellant gas with the liquid exiting from the nozzle entering aspace which is filled with gas having a temperature of at least 50 Kbelow the solidification temperature of the liquid.
 6. Process accordingto claim 1, wherein subsequent to the mixture of the propellant gas withthe fat exiting from the outlet opening of the nozzle, this mixture iscooled by gas guided in counterflow which is supplied from a counterflowunit, wherein the gas has a temperature of at least 50 K below thesolidification temperature of the liquid.
 7. Process according to claim1, wherein gas which has exited from the nozzle as propellant gas andwhich was separated from particles is compressed, cooled, andrecirculated.
 8. Process according to claim 1, wherein through acounterflow unit, a flow of gas having a temperature of at least 50 Kbelow the solidification temperature of the liquid fat is directedagainst the gas flow exiting from the outlet opening.
 9. Processaccording to claim 6, characterized in that the gas exiting from thecounterflow unit is gas which has exited the nozzle, was separated fromparticles, was compressed and cooled, and is recirculated.
 10. Processaccording to claim 1, wherein the propellant gas and/or the gas which issupplied to the counterflow unit has a temperature of at least 75 Kbelow the solidification temperature of the fat.
 11. Process accordingto claim 1, wherein the propellant gas and/or the gas which is suppliedto the counterflow unit is liquid nitrogen or gaseous nitrogen which wasgenerated immediately beforehand from liquid nitrogen.
 12. Processaccording to claim 1, wherein the propellant gas has a temperature at orabove the solidification temperature of the fat, and in that the gaswhich is supplied to the counterflow unit is liquid nitrogen or gaseousnitrogen which was generated immediately beforehand from liquidnitrogen.
 13. Process according to claim 1, wherein the nozzle is heatedat least sectionally to a temperature above the solidificationtemperature of the liquid fat.
 14. Process according to claim 1, whereinthe supply line is heated to a temperature above the solidificationtemperature of the liquid fat.
 15. Process according to claim 1, whereinthe fat is a plant-based fat or a mixture of at least two plant-basedfats.
 16. Process according to claim 1, wherein the particles are mixedinto a food mass.
 17. Device for use in a process according to claim 1,the device having a nozzle whose central channel spans open an inletopening to which a propellant gas supply line is connected, and a supplyline for a liquid discharges, the temperature of which is above itssolidification temperature, wherein a source of propellant gas isconnected to the propellant gas supply line, wherein the central channeltapers from the inlet opening to a section of smallest radius. 18.Device according to claim 17, wherein the central channel opposite tothe inlet opening has an outlet opening which is spanned open by thesecond section of the central channel, which second section adjoins thesection of smallest radius and in which second section the radiusincreases up to the outlet opening.
 19. Device according to claim 17,wherein the central channel opposite to the inlet opening has an outletopening which is located in the section of the smallest radius. 20.Device according to claim 17, wherein the propellant gas supply linedischarges into an annular opening which is limited by the inlet openingand by an annular shoulder spaced therefrom.
 21. Device according toclaim 17, wherein the distance between the supply line and the annularshoulder limiting the annular opening forms a supply air opening towhich only a conduit is connected which supplies recirculated propellantgas.
 22. Device according to claim 17, comprising a counterflow unitwhich is set up to direct a gas flow against the gas flow exiting fromthe outlet opening of the nozzle.
 23. Device according to claim 17,comprising a compressor and by a cooling device coupled downstream ofthe compressor for recirculation of propellant gas, which has exitedfrom the nozzle, to a propellant gas supply line and/or to thecounterflow unit and/or to a conduit connected to a supply air opening.24. Device according to claim 17, wherein the supply line for liquidand/or the nozzle is heatable to a temperature at or above thesolidification temperature of the liquid.
 25. Device according to claim17, wherein the nozzle has a central channel which at its first endforms an inlet opening which is spanned open by a convex face about thelongitudinal axis of the central channel, and the central channel tapersto an outlet opening arranged at its opposite second end, wherein thecentral channel from the inlet opening to a section in which the centralchannel has the smallest radius is spanned open by a face which isconvex to the longitudinal axis and which extends rotationallysymmetrically about the longitudinal axis of the central channel, andwherein the central channel terminates in its smallest radius and spansopen the outlet opening.
 26. (canceled)
 27. (canceled)